“If things are starting to get blocked and backed up in the colon, you may experience bloating,” says Randall F. Holcombe, MD, director of the University of Hawaii Cancer Center in Honolulu, Hawaii. If you’re feeling a little puffy or crampy, there are many other factors that may be to blame, but if stomach symptoms persist, see your doctor. If you start to notice a constant pain in the right side of your abdomen, that may mean the disease in the later stages and has spread to the liver, he says. (Check out these habits that help prevent colon cancer.)